The present invention relates to digital information transmission systems of the type in which groups of binary signals, or bits, are transmitted in parallel over a corresponding plurality of connecting lines between circuit units, each circuit unit normally being formed on a respective chip.
Digital information transmission circuits are used to a large extent in the fields of electronic data processing including computers and the like, automation, communications, etc. Digital systems in the above fields include, for example, digital equipment, such as those serving for data input, data storage, control mechanisms, data output and readout devices, etc. where signals exchange takes place according to a certain program.
Keyboards with coding matrices or analog/digital converters which converts analog input values into digital form are known to be used for data read-in.
Traffic between such units takes place by means of digital signals, it being most common to use a binary system to represent such information. The various units then process switching variables which can have only two values: Logic 1 and Logic 0. The two values are typically represented by different signal levels in that, for example, the Logic 1 is represented by a positive potential and the Logic 0 by a negative or zero potential. According to another possibility, Logic 1 can be represented by a signal current flowing in the positive direction and Logic 0 by a signal current flowing in the negative direction.
The number of transmission paths, or lines, which must be provided depends on the length of the binary sequence, or word, to be transmitted in parallel and N transmission paths can handle 2.sup.N different signal combinations. If, for example, a binary transmission system has four or eight transmission paths, 16 or 256 different binary signal combinations, respectively, can be transmitted therethrough.
If a large quantity of binary information is to be processed in parallel a correspondingly large number of transmission paths are required so that for the transmission of such information via electrical lines, the line networks attain considerable dimensions. With integrated circuits, known as IC's, the number of terminals is limited in most cases for reasons of standardization, reliability and economy, so that likewise the number of binary signal combinations transmitted through the circuit in parallel is limited correspondingly.
The trend is now to ever larger IC's including more and more electronic elements and functions, including multilayer circuit structures and the like, which require either a correspondingly large number of transmission connections, thus increasing the fabrication costs involved and also the dimensions of the IC's, or means on each IC for converting a large number of parallel bits into several groups which can be transmitted serially, which also increases fabrication costs and IC dimensions and, additionally, significantly reduces processing speed.
A similar situation exists in the case of the digital modules employed in the field of retail electronics. For example, the industry supplying that market considers the development of a planar screen viewer having light emitting diodes, known as LED's, to be impossible simply because of the large number of control lines required to control the LED's, given that an LED viewing screen with a resolution of only 1%, i.e. composed of a matrix having 100.times.100=10,000 LED's, requires 200 control lines for the matrix.
Even when glass fiber optics are used for the transmission of information in computers employing high bits densities, difficulties have arisen due to the required large number of transmission lines, if, for example, more than 32 to 64 LED's acting as transmitters cooperate with PIN diodes or phototransistors acting as receivers.